package com.lagou.sqlSession;


import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class simpleExecutor implements Executor{

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception{
        PreparedStatement preparedStatement = null;
        if(params != null){
            preparedStatement = getPreparedStatement(configuration, mappedStatement, params[0]);
        }else{
            preparedStatement = getPreparedStatement(configuration, mappedStatement, params);
        }
        // 5. 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();
        // 6. 封装返回结果集
        while(resultSet.next()){
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for(int i = 1; i <= metaData.getColumnCount(); i++){
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段的值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public Boolean save(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception{
        PreparedStatement preparedStatement = getPreparedStatement(configuration, mappedStatement, params[0]);
        return preparedStatement.execute();
    }

    @Override
    public Boolean update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception{
        PreparedStatement preparedStatement = getPreparedStatement(configuration, mappedStatement, params[0]);
        return preparedStatement.execute();
    }

    @Override
    public Boolean delete(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception{
        PreparedStatement preparedStatement = getPreparedStatement(configuration, mappedStatement, params[0]);
        return preparedStatement.execute();
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException{
        if(paramterType != null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作：1.将#{}使用？进行代替，2.解析出#{}里面的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql){
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }

    private PreparedStatement getPreparedStatement(Configuration configuration, MappedStatement mappedStatement, Object param) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException{
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2. 获取sql语句 : select * from user where id = #{id} and username = #{username}
        //转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        // 4. 设置参数
        //获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for(int i = 0; i < parameterMappingList.size(); i++){
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(param);
            preparedStatement.setObject(i + 1, o);
        }
        return preparedStatement;
    }

}
